1. Field of the Invention
This invention relates to portable plants for the distillation of crude oil.
2. Description of the Prior Art
Crude oil distillation units, or topping plants, are well known in the art. Such plants provide means by which crude oil feed product is heated and distilled in a distillation tower, with several cuts being taken to produce products of various boiling ranges. All crude oil refineries utilize such units as a part of their refining process. Such a unit may produce, for example, diesel oil and heavy fuel oil in final product form, whereas other products, such as gasoline, must be further refined or treated to bring them to their most valuable commercial form.
Economically it has usually been considered to be most desirable to construct refineries near the market rather than near the source of production. Thus, refineries are usually constructed close to large marketing areas, and are made to handle extremely large volumes of crude oil, for example, 250,000 barrels per day and more, thereby refining the output of entire oil fields or a number of oil fields.
These economic facts produced the anomalous situation of crude oil producing areas having to import crude oil products from a substantial distance, sometimes even from a foreign country. Accordingly, consumers in many oil producing areas found themselves paying for transporation of their crude oil to a distant refinery, and again paying for transportation of crude oil products back to their area.
As a result of this problem, various efforts have been made to construct small crude oil refining units near producing areas. An example of such a plant is described in the Dec. 31, 1973 issue of the Oil & Gas Journal, at pages 146, 147. This article describes a distillation unit mounted on a number of skids so that it could be constructed at a distant plant and easily transported to the construction site. Certain of the elements of the plant are mounted on foundations whereas other portions of the plant are skidded. These plants are intended for permanent location at the construction site.
A more portable type plant is believed to have been constructed by the United States Navy in about 1955, this plant comprising a crude oil refinery constructed on three skids. It is understood that when this plant was first started it blew up. However, at a later date it is believed to have been reassembled and it may now be in operation. Details of the construction and operation of this plant are not known.
Until the present invention, no truly portable topping plant was available. Because of the characteristics of the equipment necessary for the topping plant, it was always necessary to spread out the equipment in such a way that it could not be built compactly enough for transport over the highways, for example. Thus, it has been impossible to provide portable topping units for use at sources of small amounts of crude oil, or for use in other places where the production of crude oil products in relatively small quantities is desirable.
A major problem to overcome in the construction of such a compact unit is that of providing sufficient heat in an economical manner to raise the crude oil to the temperatures necessary for distillation. Conventional salt bath, steam, and other heaters which have heretofore been used were undesirable because of their weight, cost, and other factors. A direct fired heater could not be used because such heaters unavoidably get hot spots which cause the tubes to burn through, causing the oil being processed to be set on fire, thereby endangering the entire plant.
Another problem in such a compact plant is the necessity for a distillation tower of substantial height, e.g. 25 feet or more. Height limitations preclude the transporting on the highways of a plant which includes such a distillation tower in operating position.
Another problem encountered in seeking to operate such a portable plant is that of providing adequate power to operate all functions of the plant under all conditions of operation.
Still another problem encountered is that the crude oil feed stock to the plant cannot be relied upon to be the same at all times, since it may be necessary for the plant to handle crude stocks of a wide variety of gravities. Since no degree of uniformity can be depended upon, many problems can be anticipated in operation of such a plant with a wide variety of feed stocks.
One of the major problems encountered in seeking to construct a topping plant which can be mounted on a single skid for transport on the highways is that of providing a skid which has sufficient strength to carry the weight involved without requiring a vertical height so great as to surpass highway height limitations.